In U.S. Pat. No. 5,525,268 a standard control system for supplying humidification is described using foggers that require pressurized air and water. The air pressure is kept at a higher fixed differential pressure to that of the water pressure. The bias (the difference between the air and water pressures) is constant throughout the full modulation range of the water and air pressures as described in the U.S. Pat. No. 5,525,268, which is incorporated herein by reference thereto. The constant bias enables a precise control over the amount of fog produced by the fogger and thus the amount of humidification of a space. A constant bias signal, however, tends to limit the range of humidification modulation.